Well flow device



Sept. 18, 19 45. R 'o. WALTON 2,385,316

WELL FLOW DEVICE Filed June 9, 1944 2 Sheets-Sheet l /0 A I 5:: P 4 8 5/r 'l 3 5 5 &2 2 I 5'79 E -5 5 .66 5a j 335 z. c 2 y Robert 0. 14 0/1 00r7 INVENTOR Z BY ATTORNEY lifting fluid, such as Patented Sept. 18 1945UNITED STATE WELL rnow DEVICE Robert 0. Walton, Dallas, Tex,

Tool Corporation, Dallas, '1'e'x., a

Texas Application June 9, 1944, Serial No. 539,424

assignor tovMerla corporation of' 18 Claims. (CL 103-233) This inventionrelates to new and useful improvements in well flow devices.

The invention is a modification of and improvement on the device shownin my co-pending application, Serial No. 451,570,5flled July 2 0, 1942.

One object of the invention is to provide an improved device forcontrolling the admission of a within a well tubing or conductor forlifting or raising the liquid to the surface, said device beingparticularly adapted for use as an intermitter to intermittently admitthe lifting gas at predetermined intervals in accordance with wellconditions.

An important object of the invention is to provide a simple and emcientflow device which is constructed of a minimum number of parts, saiddevice being actuated solely by the pressure of the lifting gas, wherebya diiferential in pressures across the valve element of the device isnot depended upon to operate said valve and also whereby lifting gas isadmitted into the liquid column in the well tubing only when saidlifting gas has attained the desired predetermined pressure necessary toeffect lifting of the well fluid in said tubing.

A particular object of the invention is to provide an improved device,of the character described, having a main valve for controllingadmission of the lifting gas into the well liquid column, said valvebeing normally held in a closed position by the pressure of the liftinggas; the device also including a pilot valve which is actuated when thelifting gas reaches a predetermined pressure, said pilot valve uponactuation, relieving the pressure acting to hold the main valve closed,whereby said main valve may move to an open position and thereby admitgas to the liquid column.

Anotherobject of the invention is to provide an improved -ilow devicewhich includes a main control valve having an enlarged bellows attachedthereto, both the valve head and the interior of said bellows beingexposed to the pressure of the lifting gas so that the largercross-sectional area of the bellows is utilized to normally hold. the.

valve in its closed position; the device also including means for"bleeding off" the pressure within said bellows to allow opening of themain valve when the lifting'gas reaches a predeter mined desiredpressure.

Still another object of the invention is to provide an improved flowdevice, of the character described, wherein the gas pressure acting upongas, into a liquid column the main valve bellows is bled off into thewell tubing and also wherein the means for permitting the escape of saidpressure is a pilot valve which is itself actuated by the pressure ofthe lifting gas. A specific object of the invention is to provideimproved pilot valve arrangement for controlling actuation of the mainvalve, said pilot including a depre'ssibie bellows which has itsexterior exposed to the pressure of the lifting gasso as to be actuatedthereby; the interior-of said bellows having means for limiting 'itsmovement, whereby a positive stop for movement of the valve is had andrupturing of-the bellows by an excessive lifting gaspressure isprevented.

A still further object of the invention is to provide an improved pilotvalve arrangement for-a flow device, wherein the actuating bellows ofsaid valve has a suitable liquid contained therein, said bellowsfunctioning as a positive step to limit movement of the valve and alsoacting to prevent collapse or rupturing of said bellows by excessiveexternal pressures.

The invention will be more readily understood froma reading ofthefollowing specification and by reference to the accompanyingdrawings, wherein an example of the invention is shown, and wherein:

Figure 1 is a view, partly in section and partly in elevation of awellbore having a well tubing extending therethrough showing a plurality offlow devices, coiistrucmccordance with the invention, mounted in saidtubing,

Figure 2 is an enlarged, transverse, vertical sectional view of the flowdevice, with the main 40 sectional views, taken on the lines V borehaving a well casing said tubing. attached thereto.

valve and pilot valve closed,

Figure 3 is a similar view, with the main valve closed and the pilotvalve open,

.. Figures 4 to 7 are enlarged, horizontal, cross- 4-4, 5-5, H, and 1-1,respectively, of Figure 2,

Figure 8 is a view, partly in section and partly in elevation of theflow device and showing the pilot valve closed with the main valve open,and

Figure 9 is an enlarged. transverse, sectional view of the bellowawhichact-uates the pilot valve.

In the drawings, the letter A designates a well 10 mounted-therein. Awell tubing H extends downwardly through the casing ill and hasits.upper end supported in the usual easing head I! which is mounted onthe upper endmfsaid casing. The lower end of the well'tubing has theconventional well screen l3, through which the welLfiuids are admittedinto A suitable "well v I casing l and the bore of packer II which isschematically illustrated packs oil between the tubing and casing abovethe perforated screen i3.

A plurality of valve devices B, constructed in accordance with theinvention, are connected in the tubing H and are located at variouselevations or levels therein. As will be hereinafter described, eachdevice B is adapted to control the admission of a lifting fluid, such asgas, into the well tubing string and such fluid is utilized to lift thewell liquids upwardly through the well tubing to the surface. Theinvention will be herein describedas operating with an auxiliary liftingfluid such as gas, but it is noted that the lifting fluid may be gasfrom a sub-surface formation which enters the well casing. When auxwell.

The devices B are all of identical'construction and each device includesa tubular housing which is constructed of three sections, an uppersection [1, an intermediate section I! and a lower section I9 (Figure2). The lower section i provided with an axial bore 28 and areducedcounterbore 21 which communicates with the main.

bore is formed at the upper portion of the section. .A collar 22 Havingan inlet port 23 extending therethrough is threaded into the lower endof the bore' 20 and the extreme upper end of the port has an annularbeveled valve seat 24 surrounding the same. Manifestly, the inlet port23 establishes communication between the well is of the device.

Communication between the bore 20 of said section and the interior ofthe well tubing H is established by means of a tubular nipple 25 whichextends radially from the lower portion of the section l8 and which issuitably secured within an opening 26 in the tubing. Thus a flow offluid from the annular space between the casing l0 and tubing H mayoccur through the port 23, bore 20 and nipple 25 into the interiorof thewell tubing.

For controlling the flow of fluid through the port 23, a main valve 21is mounted within the section l9 and is adapted to engage the annularvalve seat 24. The valve includes a valve head 28 and valve stem 29, thelatter having its upper end secured to the lower end of a main valvebellows 30. The upper end of the bellows is fastened to an annularcollar 3| which surrounds the lower end of the counterbore 2! and thebellows is constructed so that its spring actionnormally urges it towarda collapsed or depressed position, whereby the bellows tends to hold themain valve in a raised or unseated position, as shown in Figure 8. Forexpanding the bellows to move the valve downwardly to a seated or closedposition, the interior of said bellows is exposed to the pressureexteriorly of the device through a gas supply passage 32 which extendsradially through the upper portion of the section l8 and whichcommimicates with the counterbore With this arrangement, the pressure'ofthe the lower section fluid within the casing outside of the tubing actsagainst the interior of the bellows 30 and also acts against the valvehead 28 when the latter is seated; however, since the cross-sectionalarea of the bellows is greater than the exposed portion of the valvehead, it is evident that the valve will be held in a closed or seatedposition.

The pressure within the casing which is acting upon the bellows 30 isthat of the lifting fluid or gas and when this pressure reaches apredetermined point, it is desirable to open the main valve to admit thelifting fluid into the well tubing to effect raising of the well liquidwithin said tubing. In order to actuate the main valve 21 and move it toits unseated or open position when the lifting fluid reaches apredetermined pressure, a pilot valve 33 is mounted within the bore 34of the intermediate section IS. The pilot valve is adapted to engage avalve seat 35 which surrounds the upper end of the counterbore 2| andwhen said valve is seated the pressure is trapped within the bellows 30to hold the main valve 28 in its lowered or closed position. Upwardmovement of the pilot valve 33 opens the counterbore 2| and permits thepressure within the bellows 30 to escape upwardly into the section H;the section l8 communicates with the interior of the well tubing througha tubular nipple 36 and it is noted that the bore 31 of the nipple is ofconsiderably larger diameter than the supply passage 32 through whichthe fluid pressure is admitted to the bellows.

Therefore, as soon as the pilot valve 33 is opened, the pressure mayescape from the interior of the bellows through the counterbore 2i andnipple 36 at a faster rate than such pressure can be replenished throughthe relatively small passage 32, with the result that the pressureacting on the interior of the bellows is reduced to the point wherethemain valve 21 is opened. This opening of the main valve is effected bythe normal collapsing action of the bellows and also by the liftingfluid acting against the lower end of said valve.

In order to open the pilot valve 33 when the pressure of the liftingfluid reaches the predetermined desired point, said valve is actuatedsolely by the lifting fluid pressure. As is clearly shown in Figures 2and 3, the pilot valve includes a stem 38 which extends upwardly througha reduced counterbore 39 formed in the lower portion of the uppersection [1. A suitable packing ring 40 is disposed within a recess 4| inthe counterbore and surrounds the stem to seal off around said stem, Theupper end of the stem extends upwardly into the main bore 42 of thesection 11 and has itsextreme upper end fastened to a plug whereby thepilot valve attached to its lower end is normally urged toward itsseated position.

'Infiijt nor of the bellows is filled (Figures 2 and 9) with a suitablefluid such as water or oil and the upper end of said bellowscommunicates with a recess 43 in the cap member 46. When the bellows isexpanded and the pilot valve seated (Figures 2 and 9) the fluid does notcompletely fill the recess, whereby the bellows may be depressed untilthis recess is completely filled as illustrated in Figure 3. The volumeof fluid within the bellows will determine the amount of movement whichthe bellows may undergo and thus the fluid acts as a positive stop tolimit the travel of the pilot valve. Also, it is apparent that when thebellows is fully depressed the fluid completely fills. said bellows andrecess and since said fluid breaking of the bellows by an excessiveexternal pressure on said bellows cannot occur. Thus,

' the fluid not only acts as a stop for limiting movement of the pilotvalve but also acts to prevent rupturing of said bellows by externalpressure and this is an important feature-of the invention.

In addition to the normal action of the bellows urging the pilot valveto its seated position, a

coiled spring 48 surrounds the pilot valve stem 38 within the uppersection II. This spring has its lower end engaging an external annularflange or ring 49 which is secured to the stem, while its upper end isconfined against the lower end of a fixed sleeve 5 0. The sleeve 50 hasits upper end fastened to the cap member 46 and encircles the pilotbellows 44. The plug 43 which closes the lower end of the bellows andhas" the stem attached thereto is arranged to engage the flanged lowerend of the sleeve when the pilot valve is in a lowered or closedposition (Figure 2). The sleeve 50 has a plurality of ports or openings5! therein while the upper section is provided with inlet ports 52whereby the pressure of the lifting fluid in the casing may enter thesection and then the sleeve to act upon the bellows 44- to depress thesame. It is noted that the sleeve 50 could be replaced by elongate stoparms which would serve the same purpose.

The spring 48 which urges the pilot valve to its closed position is of apredetermined tension and obviously, the pressure of the lifting fluidacting against the pilot bellows 44 must reach a predetermined pressurebefore the pilot valve will open. By changing the tension of thisspring, the pilot valve may be arranged to open at any desired liftingfluid pressure. No difl'erential of pressure across the valve isdepended upon because the spring exerts a constant fixed pressure on thevalve which can be overcome only when the lifting fluid pressure exceedssuch constant.

In operation, a plurality of valve devices B are connected in the tubingstring H and are disposed at various elevations therein. Each valvedevice has its spring 48 properly adjusted so as to exert apredetermined pressure upon its is non-compressible,- rupturing or pilotvalve 33, it being preferable that the uppermost device be set for thehighest pressure. For example, the uppermost valve device in the tubingmay be set to open the pilot valve at 450 pounds per square inch, thenext set to open at 425 pounds, the third at 400 and so on progressivelyto the lowermost device in the tubing which would, of course, beoperated by the lowest pressure.

With no or insufllcient pressure in the well casing. each valve deviceis in the position shown in Figure 8 with the main valve 21 open and thepilot valve 33 closed. To initially start the devices in operation, thelifting fluid is introduced into the casing until suflicient pressure toextend the main valve bellows so has been introduced. It is noted thatthe pilot valve spr 43 exerts a greater pressure than the main valvebellows 30 so that said bellows is extended to close the main valvebefore the pilot valve opens. The introduction of the initial liftingfluid may be accomplished either by closing in both tubing and casingand equalizing pressures throughout and then bleeding oil the tubingpressure to hold a sufllcient pressure in the casing to maintain themain valve 21 seated, or by admitting the lifting fluid pressure intothe casing in 8. vol ume greater than the fluid can escape into thetubing through the open main valves of the various devices. In thislatter method, it is anparent that the pressure will be built up in thecasing until it becomes sufficient to close the main valve through itsaction on the main valve bellows 30. When this point is reached, noadditional lifting fluid is admitted except at the proper intervals bythe intermitter.

As explained. the pressure of the lifting fluid acts through the passage32 and counterbore 2| and against the interior of the main valve bellows30 to hold the main valve 21 seated or closed. At this time, the pilotvalve 33 is also closed since the spring 48 has a greater pressure thanthe spring action of the main bellows.

The liquid column in the well tubing is permitted to build up to itsstanding level after which the intermitter l6 actuates to' admit acharge of lifting fluid to increase the pressure of said fluid withinthe casing. ,As this pressure reaches the point at which the uppermostvalve is set, said pressure acting through the ports 52 in the sectionII and portsll in the sleeve 50 overcomes the tension of the spring 48anddepresses the pilot valve bellows 44 to raise the pilot valve 33 fromits seat. As soon as this occurs the pressure within the main valve"bellows 30 may escape through the counterborejl and nipple 36, with theresult that the main valve 21 is unseated (Figure 3) to admit thelifting fluid into the tubing through inlet port 23 and nipple 25. Thislifting fluid will lift the well liquidto the surface in the usualmanner. The main valve 21 will remain open so long as the pressureacting upon the pilot bellows 44 is suflicient to hold the pilot valveopen against the pressure of the spring 48. However, when the fluidpressure in the casing drops below the pressure of the spring 48 thepilot valve closes to again trap the pressure within the main valvebellows and thereby close the main valve.

The particular adjustment of the valve devices which sets the uppermostvalve to operate at the highest pressure with each valve devicetherebelow set for progressively lower pressures also makes it possibleto efiect a lowering of the working level of the well, whereby a lowerlifting fluid pressure is required for lifting purposes. When utilizedin this manner, the tubing string having the valve devices connectedtherein is lowered into the well and for purposes of illustration, itwill be assumed that the well is 5,000'feet deep with a normal standingliquid level of 4,000 feet, which means that the normal level is 1,000feet below the surface. The well packer I4 is then set within the wellcasing and obviously, a column of liquid is trapped in the annular spacebetween the well tubing and casing. Due to the construction of the'valvedevices, those devices which are subjected toijiressure greater thanthat for which their respective pilot bellows are adjusted are held openby the pressure exerted by the liquid column. Those devices nearer theupper end of the column which are not subjected to suflicient pressureto open their pilot valves may be held in a closed position or if suchpressure is insuflicient to extend the main bellows 30, the valve may beopen. 1

After the packer is set, the auxiliary lifting fluid pressure isintroduced into the annular space between the tubing and casing and theadmission of the initial pressure will be suflicient to effect closingof all of the uppermost valves above the point at which the liquidcolumn exerts a pressure suflicient to hold the valves therebelow in aclosed position, with the uppermost valve device adjusted to be openedwhen the pressure in the annular space between casing and tubing reaches450 pounds, the lifting fluid is admitted into the casing until thispressure is reached; since all of the valve devices below the uppermostone are adjusted to open at lower pressures,

it is apparent that when 450 pounds pressure is reached, all of saiddevices will be open. When the uppermost valve device opens, the liftingfluid is admitted to the well tubing and lifts the well liquid in thetubing above this valve device to the surface, whereby the upper portionof the liquid column in said tubing is raised. This removal of a portionof the liquid column lightens the load ;,in the well tubing and allowsthe well liquid to flow from the annular space between the casing andtubingand intothe tubing, thereby lowering the liquidlevel in theannular space and raising the level ,inlthe tubing above the uppermostvalve, so ,thatas' the ,intermitter shuts off :flow, the uppermost valvecally admits 'lifting'fluid, the uppermost valve continues to operateuntil the liquid level in the casing orannular'space has been lowered topermitj the lifting fluid to reach the next below valve device.

After this next device is reached, it will continue to pass liftingfluid until the intermitter l6 shuts off the admission of lifting fluid,at which time the. pressure within the tubing and casing will equalizeback to the operating pressure of said second valve which, as presumed,is 425 pounds. Because theuppermost valve is set at s 450 pounds, saidvalve will close and will remain so. Subsequent admission of liftingfluid will actuate the second valve to lift additional liquid from thetubing and thereby further lower the level in the annular space untilsuch time as the next below valve device is reached, after which thelifting of liquid is accomplished at the operating pressure of thelatter valve device. The operation is continued until the bottom orlowermost valve device, which operates at the lowest pressure is reachedand from this point on, the

- lowermost valve will function to admit the lifting fluid into thetubing to raise the well liquids entering the tubing from the formation.Thus, operation will continue from the lowermost valve at its operatingpressure and theupper valves will remain closed. The arrangement permitsthe working level of the well to be lowered and thereby allows the wellliquids to be lifted to the surface with a minimum operating pressure.

It is pointed out that the pilot, bellows 44 is filled with a fluidwhich as explained, acts as a stop or limiting means to limit upwardmovement of the pilot. Ihe'bellows completely seals its interior and theadjacent recess 48 to a constant pressure within the pressure range ofthe valves operation. It is pointed out that when the valves are firstrun into a well having well fluid therein the bellows are subjected tothe pressure of the liquid column which of course reflects the bottomcloses As the intermitter periodi- I hole pressure. When the necessarygas or lifting fluid pressure is applied to actuate the valves, thebellows is subjected to the combined pressure of the well liquid and gasand unless some means such as the liquid within said bellows isprovided, the bellows might be ruptured prior to operation of theapparatus. With the arrangement shown, damage to the bellows byexcessive pressures is prevented, When in its extreme depressed position(Figure 3) the fluid completely fills the bellows and thus regardless ofthe pressure which may be acting on the exterior of said bellows, thereis no danger of said bellows being ruptured.

The device is simple in construction and involves a minimum number ofparts. It is actuated solely by the pressure of the lifting gas andeliminates the necessity of depending upon a pressure differentialacross the valves for its actuation. The use of the spring 48 whichcontrols the pressure at which the device operates makes it possible toeasily adjust the device to adapt it to particular well conditions.Although the invention has been described as operated by an auxiliarylifting fluid or gas, some wells may have sufficient gas entering thecasing from a sub-surface formation and it is within the scope of theinvention to actuate the valve devices with explanatory thereof and,various changes in the size, shape and materials-"as well as in'the'details of the illustrated construction-may be made, within thescope of the appended claims, without departing from the spirit of theinvention.

What I claim and desire to secure by Letters Patent is:

l. A flow device adapted to be connected in a well tubing and including,a housing having a flow passage for establishing communication betweenthe exterior and interior of the well tubing, a main valve element forcontrolling the flow through said passage, movable means acted upon bythe pressure of the fluid exteriorly of the tubing for normally holdingthe main valve in a seated or closed position shutting oif flow throughthe passage, and pilot valve means arranged to be actuated when thepressure exteriorly of the tubing reaches a predetermined point forreleasing the pressure acting on the movable means, whereby the mainvalve is opened to admit flow into the tubing upon the establishment ofa prelishing communication between the exterior and interior of thetubing, a main valve element within the passage and movable to open andclosed positions within said passage for controlling the flowtherethrough, pressure actuated means connected with the valve andhaving one ,side exposed to the pressure exteriorly of the tubing forimparting movement to the valve, said pressure actuated means moving thevalve to a closed position when acted upon by said pressure, andoperating means also actuated solely by the pressure ygteriorly of thetubing for releasing the pressureacting on the pressure actuated meansto effect opening of the main valve to permit a flow through the passageand into the tubing.

3. A well flow device as set forth in claim 2, wherein the operatingmeans is actuated only 4. A well flow device as set forth in .=aim 2,

- wherein the operating means is a puntvar-c arrangement which isnormall clues o pre ent escape of the pressure acting on the pressureactuated means and when opened releases such pressure to permit openingof the main valve.

5. A well flow device adapted to be connected in a. well tubing andincluding, a housing having a flow passage establishing-communicationbetween the interior and exterior of the tubing, 9.

' -main valve within the passage and movable to open and closedpositions therein for controlling flow therethrough, a flexibleoperating element connected with the main valve and having its interiorexposed to the pressure exteriorly of the tubing whereby said element isactuated to hold the main valve in a closed position, the housing havingan enlarged escape port extending from the element to permit escape ofthe pres-' sure acting thereon to allow opening of the main valve, and apilot valve actuated solely by the lifting fluid pressure forcontrolling the flow through said escape port, whereby said pilot mustopen before the pressure acting on the operating element can be releasedto open the main valve and admit flow into the tubing.

6. A flow device as set forth in claim 5, wherein the pilot valve isnormally in a closed position and is moved to an open position only whenthe pressure exteriorly of the tubing reaches a predetermined point.

I. A well flow device adapted to be connected in a well tubing andincluding, a housing having a flow passage-establishing communicationbetween the interior and exterior of the tubing, a main valve within thepassage and movable to open and closed positions therein for controllingflow therethrough, a flexible operating element connected with the mainvalve and having its interior exposed to the pressure exteriorly of thetubing whereby said element is actuated to hold the main valve in aclosed position, the housing having an enlarged escape port extendingfrom the element to permit escape of the pressure acting thereon toallow opening of the main valve, a pilot valve for controllin the flowthrough said escape port, whereby said pilot must open before thepressure acting on the operating element can be released to open themain valve and admit flow into the tubing. and a pressure operated meansexposed to and actuated by the pressure exteriorly of the tubing formoving the pilot valve to an I open position.

8. A well flow device adapted to be connected .in a well tubing andincluding, a housing having 8. flow passage establishing communicationbetween the interior and exterior of the housing, a

' main valve within the passage and movable to thereof exposed to thepressure exteriorly of.

the tubing whereby such pressure holds the main valve seated, thehousing having a release port for permitting escape of the pressureacting upon the valve actuating means whereby the main valve is openedwhen said pressure is released, a. pilot valve normally closing therelease port, and means exerting a predetermined pressure on the pilotvalve and urging it to a closed position, whereby the pressureexteriorly of the tubing must reach a predetermined point before thepilot is opened to permit opening of the main valve,

10. A well flow device adapted to be connected a well tubing andincluding, a housing having a flow passage establishing communicationbetween the interior and exterior of the housing, a main valve withinthe passage and movable to open and closed positions therein forcontrolling flow. therethrough, valve actuating means connected withsaid valve and having one side thereof exposed to the pressureexteriorly of the tubing whereby such pressure holds the main valveseated. the housing having a release port for permitting escape of thepressure acting upon the valve actuating means whereby the main valve isopened when said pressure is released, a pilot valve normally closingthe release port. an actuating bellows connected to the pilot valve fortmpart-.

ing movement thereto. said bellows being nor- 0 when the latter isexpanded and completely fillof exposed to the pressure cxteriorly of thetub-,'

lng whereby such pressure holds the mainvalve seated, the housing havinga release port for permitting escape oi the pressure acting upon thevalve actuating means whereby the main valve is opened when saidpressure is released. a pilot valve normally closing the release port.and an -operating bellows connected to the pilot valve and exposed tothepressure extcriorly of the tublng so as to be actuated thereby.

9. A well flow device adapted to be connected in a well tubing andincluding, a housing having ing said interior when depressed, wherebythe liquid functions as a. stop to limit depression of the bellows andalso acts to prevent rupturing of the bellows by excessive externalpressure.

ll. Allow device as set forth in claim 9. together with a. liquid withinthe operating bellows. said liquid completely filling the interior ofthe bellows after the same has been actuated, whereby said liquid notonly limits the movement of the bellows but also protects the same fromcollapse and rupture due to excessive external pressures.

12. A flow device as set forth in claim 9, wherein the means exerting apredetermined pressure on the pilot valve is a spring.

13. A well flow device as set forth in claim 7. wherein the pressureoperated means is an operating bellows. together with a liquid withinsaid bellows, said liquid completely filling the interior of the bellowsafter the same has been actuated, whereby said liquid not only limitsthe movement of the bellows but also protects the same from collapse andrupture due to excessive external pressure.

14. A well flow device as set forth in claim 1. wherein the pilot valvemeans is connected to a bellows which is exposed to and actuated by thepressure exteriorly of the tubing, said bellows having its interiorpartially filled with liquid when in an extended position and havingsaid interior completely filled when in a retracted position, whgrgbysaid liquid functions to limit movementnfsth bellows and also to preventrupturing thereof by external pressures.

15. A well flow apparatus including, a well casing, a well tubingextending axially through the casing and having a well liquid inlet atits lowerend, means for introducing a lifting gas underai pressure intothe annular space between the easing and tubing, and a plurality of flowdevices 5 mounted in the tubing, each device having a flow passage forestablishing communication between the casing and tubing and having amovable main valve element and also having a movable pilot valve, saidmain valve element being held closed 10 by the pressure in the wellcasing and being adapted to be opened solely by the'casing pressureacting upon the pilot valve which pilot valve releases the pressureholding said movable main valve closed, each device having its pilotvalve la 16. A well flow apparatus as set forth in claim 15, wherein theflow devices are spaced throughout the length of the tubing and whereinthe uppermost device is set to operate at the highest pressure with theremaining devices being set at successively lower pressures with thelowermost device operating at the lowest pressure.

17. A well fiow apparatus as set forth in claim 15, wherein the movablevalve element has an operating bellows connected therewith with theinterior of said bellows exposed to the casing pressure.

18. A well flow apparatus as set forth in claim 15, wherein the pilotvalve is connected with a bellows having its exterior exposed to thecasing pressure. whereby when said pressure attains a predeterminedpoint the bellows is compressed to actuate the pilot and thereb permitopening of the movable valve element.

ROBERT O. WALTON.

